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copied!<p><img src="https://i.stack.imgur.com/9YeOU.png" alt="Racing UI"></p> <p>I made a number of changes. Here are some I can recall.</p> <ol> <li>Refactored custom painting from top-level container to <code>JPanel</code>, and moved painting to <code>paintComponent()</code>.</li> <li>Removed <code>Thread</code> and <code>Thread.sleep(n)</code> & replaced with a <code>Timer</code>/<code>ActionListener</code>.</li> <li>Constructed the GUI on the EDT.</li> <li>Removed setting the size of the <code>JFrame</code>. Instead sets a preferred size for the <code>JPanel</code> (the actual drawing area) and calls <code>JFrame.pack()</code> to get the correct overall size.</li> <li>Uses <code>setLocationByPlatform(true)</code> instead of the <a href="https://stackoverflow.com/a/7143398/418556">very splash-screen like</a> <code>setLocationRelativeTo(null)</code>.</li> </ol> <p>Check the code carefully for further tips.</p> <pre><code>import javax.swing.*; import java.awt.*; import java.awt.event.*; public class Racing extends JPanel implements KeyListener { private static final long serialVersionUID = -198172151996959655L; //keeps track of player speed double plSpeed = .5; //numbers that represent direction final int UP = 0, RIGHT = 1, DOWN = 2, LEFT = 3, STOP = 5, START = 6; //keeps track of player direction int p1Direction = START; //makes player 1's car Rectangle p1 = new Rectangle ( 100, 25, 30, 30 ); //constructor public Racing() { //define defaults for the JFrame setBackground(Color.BLACK); //makes the screen size setPreferredSize(new Dimension(400,50)); //makes the key listener "wake up" addKeyListener(this); setFocusable(true); ActionListener al = new ActionListener() { public void actionPerformed(ActionEvent ae) { //refresh screen repaint(); //makes car increase speed a bit if (plSpeed <= 7) { plSpeed += .2; } //lets the car stop if (plSpeed==0) { p1Direction = STOP; } //moves player based on direction if (p1Direction==UP) { p1.y -= (int) plSpeed; } if (p1Direction==DOWN) { p1.y += (int) plSpeed; } if (p1Direction==LEFT) { p1.x -= (int) plSpeed; } if (p1Direction==RIGHT) { p1.x += (int) plSpeed; } if (p1Direction==STOP) { plSpeed = 0; } } }; Timer t = new Timer(75,al); t.start(); } //draws the cars and race track @Override public void paintComponent(Graphics g) { super.paintComponent(g); //draw p1 g.setColor(Color.RED); g.fillRect(p1.x,p1.y,p1.width,p1.height); } //have to input these (so it will compile) public void keyPressed(KeyEvent event) { System.out.println(event); try { //makes car increase speed a bit if (event.getKeyChar()=='w' || event.getKeyChar()=='a' || event.getKeyChar()=='s' || event.getKeyChar()=='d') { plSpeed += .2; //repaint(); } } catch (Exception I) {} } public void keyReleased(KeyEvent event) {} //now, to be able to set the direction public void keyTyped(KeyEvent event) { if (plSpeed > 0) { if (event.getKeyChar()=='a') { if (p1Direction==RIGHT) { p1Brake(); } else { if (p1Direction==LEFT) { } else { p1Direction = LEFT; } } } if (event.getKeyChar()=='s') { if (p1Direction==UP) { p1Brake(); } else { if (p1Direction==DOWN) { } else { p1Direction = DOWN; } } } if (event.getKeyChar()=='d') { if (p1Direction==LEFT) { p1Brake(); } else { if (p1Direction==RIGHT) { } else { p1Direction = RIGHT; } } } if (event.getKeyChar()=='w') { if (p1Direction==DOWN) { p1Brake(); } else { if (p1Direction==UP) { } else { p1Direction = UP; } } } if (event.getKeyChar()=='z') { p1Brake(); } } } public void p1Brake () { try { while (plSpeed != 0) { plSpeed -= .2; } } catch (Exception e) { plSpeed = 0; } } //finally, to start the program public static void main(String[] args) { SwingUtilities.invokeLater( new Runnable() { public void run() { JFrame f = new JFrame("Racing"); f.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE ); f.add(new Racing()); f.pack(); f.setLocationByPlatform(true); f.setResizable( false ); f.setVisible( true ); } }); } } </code></pre>

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